This invention relates to the field of network simulation, and in particular to the modeling of MAC (media access control) and PHY (physical) layer interfaces for wireless devices.
The use of wireless devices continues to grow and wireless networks have entered the realm of commercial communication systems. Traditional communication and information processing issues regarding configuration control and communications efficiency, which had heretofore been generally limited to wired networks, are now being addressed for managing wireless networks.
One of the fundamental tools available to a network manager for network planning, diagnostics, and control is a network simulator. The interconnection of elements forming a network is modeled, and hypothetical traffic patterns are provided to the model to determine and/or estimate how the modeled network will perform under these traffic conditions. Alternative interconnections and/or configurations of the elements can also be modeled, to perform a “what-if?” analysis, or to diagnose real or assumed problems in the network.
Conventional system simulators typically use fairly primitive models of wireless devices or wireless sub-networks, because the likelihood of a wireless device or sub-network having an impact or effect on the performance of traditional mainstream networks is minimal. When accurate simulation of wireless network performance is required, the device models are complex and difficult to parameterize, because the number of factors that can affect the communication of messages in a wireless network are substantially greater than those that might affect a similarly structured wired network. Complex models provide more fidelity in the results, at the cost of slowing simulation performance. Additionally, because wireless devices are typically mobile devices, a wireless network's dynamic structure is generally too fluid for static modeling in a conventional network simulator.
It is an objective of this invention to provide a method and system that accurately models the performance of wireless networks. It is a further objective of this invention to provide a method and system that accurately models the propagation of packets between and among mobile wireless devices. It is a further objective of this invention to provide a method of modeling and simulating wireless devices that minimizes the parameters required at each wireless device. It is a further objective of this invention to provide a framework that can be adapted to simulate the behavior of different MAC protocols under different physical layer characteristics. It is a further objective to achieve acceptable simulation performance compared to the real time performance of the actual wireless networks.
These objectives, and others, are achieved by a simulation model that effectively emulates a variety of phenomena that affect transmissions via a wireless media. Such phenomena include media access contention delays, packet drops, and changes in transmission/reception locations. Each wireless environment is characterized by a model that characterizes transmission effects based on the number of competing transmitters in the environment. Because the wireless devices may be mobile, the number of competing transmitters is dynamically determined based on the location of each device in the environment and its associated traffic activity. Additionally, the location of devices is used to model the effects of ‘hidden nodes’, nodes that are unknown to a transmitter but can interfere with the reception of transmissions at a receiver. In a preferred embodiment, each device model in the wireless environment accesses the same model that characterizes the environment, thereby minimizing the amount of detail required at each device model.
Throughout the drawings, the same reference numerals indicate similar or corresponding features or functions. The drawings are included for illustrative purposes and are not intended to limit the scope of the invention.